The long-term goal of this project is to determine if Parotid Secretory Protein (PSP; SPLUNC2) is a dual function host-defense protein in the oral cavity. PSP is expressed in salivary glands, oral epithelial cells and saliva but its function is unknown. Expression of PSP is up-regulated by bacteria and TNF and an in silico structural analysis of PSP revealed that it may be similar to bactericidal/permeability increasing protein (BPI) and LPS-binding protein (LBP). Guided by the location of active domains in these two proteins, several PSP peptides were designed and found to exhibit both antibacterial and anti-endotoxin activities in vitro and in vivo. Based on these initial results with PSP peptides and additional preliminary data for intact PSP it is hypothesized that the dual- function antibacterial and anti-inflammatory activities detected for PSP peptides are reflected in the biological activity of the intact PSP protein. Two specific aims will test the proposed functions of PSP. Aim 1 will characterize the antibacterial activity of PSP. PSP peptides and recombinant PSP will be used in biochemical, cell biological and in vivo experiments to determine if PSP exhibits bacteriostatic or bactericidal activity, bacterial agglutination, and inhibition of biofilm formation. Aim 2 will characterize the anti- inflammatory activity of PSP. PSP peptides and recombinant PSP will be used in biochemical, cell biological and in vivo experiments to determine if PSP binds LPS, blocks the action of LPS in vitro and protects mice in an LPS-induced sepsis model. If confirmed, the proposed functions of PSP will expand the group of antimicrobial host- defense proteins that are expressed in the oral cavity and participate in the defense of the oral mucosa. Thus, the research proposed here will lay the foundation for future translational research aimed at novel clinical approaches to combat infection and control inflammation.